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Group 1 – EFP | Poster Abstracts
the estimation of ETAS models, which are conventionally estimated by maximum likelihood.
Under suitable conditions such a procedure produces estimates that have desirable asymptotic
properties such as unbiasedness, consistency, and efficiency. In practice, however, earthquake
catalogs are typically limited only to earthquakes above some lower threshold magnitude, and the
fact that many smaller events are not observed can lead to substantial biases in the estimation of
ETAS parameters.
1-094
WHY BASS, NOT ETAS Turcotte DL, Van Aalsburg JD, Abaimov SG, and Rundle JB
What is the ETAS model? It is a stochastic model for the generation of aftershock sequences. It is
based on the concept of parent and daughter earthquakes. The number of daughter earthquakes
that a parent earthquake generates is determined randomly from a productivity relation. The
magnitude and time of occurrence of each daughter earthquake is determined randomly from the
Gutenberg-Richter and Omori laws. Each first generation daughter earthquake becomes a parent
for second generation daughters, and so forth until the sequence dies out. What is the BASS model?
The BASS model is the self-similar limit of the ETAS model. Instead of the productivity relation,
the modified form of Bath's law is used. The two arbitrary parameters in the productivity relation
are replaced by the b-value in the GR law and the magnitude difference Delta m* between the
parent earthquake and the largest expected daughter earthquake. Why is the BASS model
preferred to the ETAS model? Because the BASS model is in better agreement with observations
than the ETAS model. Specifically: (1) The BASS model generates Bath's law statistics since they are
an input; (2) The BASS model generates inverse GR statistics for foreshock generation. The
distribution of magnitudes of foreshocks is independent of the mainshock magnitude. The ETAS
model has an exponential dependence of foreshock magnitude on the mainshock magnitude which
is not in agreement with observations. Why do ETAS model proponents reject the BASS model?
Because the BASS model is inherently unstable generating infinite numbers of aftershocks.
However, this instability is easily removed by making the physically reasonable hypothesis that the
excess magnitudes of daughter earthquakes over the parent earthquake cannot exceed a specified
difference.
1-095
EXTENDING THE CISN EARTHQUAKE EARLY WARNING (EEW) WEB SITE INTO
THE CISN EEW TESTING CENTER USING CSEP TESTING CENTER CONCEPTS
AND SOFTWARE Zeleznik MP, Maechling PJ, Liukis M, Callaghan S, Boese M, Hauksson E,
Cua G, Solanki K, Allen RM, Neuhauser D, Hellweg M, Fischer M, Heaton TH, and Jordan TH
As a part of the California Integrated Seismic Network (CISN) earthquake early warning (EEW)
algorithm development, funded through USGS NEHRP, we have developed the CISN EEW web
site to collect the results of multiple EEW algorithms and to display these results in a comparative
manner (http://www.scec.org/eew). During the last year, the CISN EEW algorithm development
group defined a set of EEW algorithm evaluation tests (termed performance summaries). These
compare EEW algorithm reports (generated by the real-time or near real-time EEW algorithms)
against seismicity data in the ANSS catalog and observed ground motion information available
through the SCEC Data Center (SCECDC) and the Northern California Earthquake Data Center
(NCEDC). To automatically generate the performance summaries, a software development group
at SCEC has integrated elements of the SCEC Collaboratory for the Study of Earthquake
Predictability (CSEP) Testing Center into the CISN EEW web site. This has helped establish a CISN
EEW Testing Center with capabilities similar to the CSEP Testing Center. After the integration of
the CSEP software, the CISN EEW testing center now automatically creates EEW performance
summaries and posts them on the CISN EEW web site each day.By leveraging the capabilities of
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